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Properties of Arc-Melted Chromium-Base Alloys

Description: From abstract: "Twelve binary chromium-base alloy systems were screened for hot workability, oxidation resistance, and hot strength using small ore-melted ingots...Experiments with the preparation of large chromium-base alloy ingots showed that cold-mold ore melting was not suitable for preparing ingots containing over about 1 w/o of alloy addition."
Date: July 14, 1958
Creator: Maykuth, Daniel J.; Roberts, John W., Jr. & Jaffee, Robert Isaac
Partner: UNT Libraries Government Documents Department

Preparation and Properties of the Eutectic Uranium-Chromium Alloy

Description: This report follows the study of the properties of eutectic uranium-chromium alloy which is of interest in the Dow-Detroit Edison power reactor. The reactor is described in this report, as well as the casting of alloy, shrinkage measurements during solidification, density measurements, microstructures and macrostructures, mechanical properties, and specific heat data.
Date: November 3, 1953
Creator: Saller, Henry A.; Rough, Frank A. & Dickerson, Ronald F.
Partner: UNT Libraries Government Documents Department

Ductilization of Cr via Oxide Dispersions

Description: Work by Scruggs et al. in the 1960's demonstrated that up to 20% tensile ductility could be achieved at room-temperature in sintered and extruded powder metallurgical Cr alloyed with MgO. During sintering, much of the MgO converts to a MgCr{sub 2}O{sub 4} spinel, which was hypothesized to getter nitrogen from the Cr, rendering it ductile. Recent efforts at Oak Ridge National Laboratory (ORNL) have succeeded in duplicating this original effect. Preliminary results suggest that the ductilization mechanism may be more complicated than the simple nitrogen gettering mechanism proposed by Scruggs, as some ductility was observed at room-temperature in Cr-MgO alloys containing nitride precipitates. Results of microstructural characterization and room-temperature mechanical property studies are presented for Cr-6MgO-(0-2.2)Ti wt.% as a function of hot-pressing and extrusion. Possible mechanisms by which the MgO additions may improve the room-temperature ductility of Cr are discussed.
Date: February 14, 2001
Creator: Brady, M.P.
Partner: UNT Libraries Government Documents Department

Thermal Conductivity of Uranium-Chromium and Uranium-Iron Eutectic Alloys

Description: Report discussing measurements of thermal conductivity and heat capacity for uranium-chromium and uranium-iron eutectic alloys at room temperature. The resulting values were intended for use in design calculations until more accurate data at other temperatures was obtained.
Date: April 14, 1953
Creator: McKee, John M., Jr.
Partner: UNT Libraries Government Documents Department

Analytical prediction of the location of ductility dip cracking in the trans-varestraint test

Description: Some NiCrFe weld metals exhibit decreased ductility over a temperature range known as the {open_quotes}ductility dip{close_quotes} temperature (DDT) range. Ductility dip cracking (DDT) is a phenomenon which occurs in a zone bounded by the DDT range on its sides and a threshold plastic strain on its bottom as shown in figure 1. Figure 1 illustrates how ductility varies as weld metal cools from the solidus temperature for materials with and without a ductility dip. The purpose of this work is to demonstrate the ability to predict the location of the DDC in a Trans-Varestraint Test (TVT) for a specimen machined from a weld deposited EN52 plate. The DDC predictions require a combination of Trans-Varestraint testing and finite element analysis. The test provides the threshold value of externally applied nominal strain below which DDC does not occur. The analysis provides the corresponding threshold local or peak strain. The threshold local plastic strain level and the DDT range are used to predict the location of the DDC. The ultimate purpose of this work is to evaluate susceptibility of highly constrained, component welds to DDC. Test results for Trans-Varestraint Testing for a weld deposited EN52 plate are reported in reference. The ability to predict the location of the DDC in the Trans-Varestraint Test using the techniques reported herein is demonstrated by showing good comparison between the analytical results and the test data.
Date: May 1, 1997
Creator: Singh, I.; Kroenke, W. & Cola, M.
Partner: UNT Libraries Government Documents Department

Ultrafine fully-lamellar structures in two-phase {gamma}-TiAl alloys

Description: Special ultrafine fully lamellar microstructures have been found recently in {gamma}-TiAl alloys with 46-48% Al processed or heat treated above the {alpha}-transus temperature (T{alpha}). Hot extrusion above T{alpha} also produces a refined colony or grain size. Refined-colony/ultrafine-lamellar (RC/UL) microstructures produce an excellent combination of RT ductility and high-temperature strength in Ti-47Al-2Cr-2Nb (at.%) alloys. UL structures also have regularly alternating {gamma} and {alpha}{sub 2} lamellae, such that they are dominated by {gamma}/{alpha}{sub 2} interfaces with relatively few {gamma}/{gamma} twin boundaries. Focus of this study is on how changes in processing parameters or alloy composition affect formation of the UL structure, particularly the {alpha}{sub 2} component.
Date: December 31, 1996
Creator: Maziasz, P.J. & Liu, C.T.
Partner: UNT Libraries Government Documents Department

ALCHEMI of niobium dichrome/vanadium C15 Laves phase

Description: 33Nb42Cr25V was prepared by arc melting and annealing at 1400 C for 120 hr. Energy-dispersive x-ray spectra were collected over a range of {l_brace}400{l_brace} excitations between symmetry and beyond {l_brace}12 0 0{l_brace}. Results show that at least qualitatively V substitutes for Cr. Therefore, electronic effects must be more important than size effects in this case.
Date: May 1, 1996
Creator: Kotula, P.G.; Chu, Fuming; Mitchell, T.E.; Anderson, I.M. & Bentley, J.
Partner: UNT Libraries Government Documents Department

Strain measurements in thermally grown alumina scales using ruby fluorescence

Description: We have measured strains in alumina scales thermally grown on Fe-Cr- Al alloys by exploiting the strain dependence of the ruby luminescence line. Measurements were done on Fe-5Cr-28Al and Fe-18Cr-10Al (at.%, bal. Fe) oxidized between 300-1300 C with periodic cycling to room temperature. Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a dilute reactive element (Zr or Hf) are also presented. We observe that scales on alloys containing a reactive element (RE) can support higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed. In early stage oxidation, the evolution of transition phases is monitored using Raman and fluorescence spectroscopies. The fluorescence technique also provides a sensitive probe of early stage formation of {alpha}-Al{sub 2}O{sub 3}. It appears that, in presence of Cr{sub 2}O{sub 3} or Fe{sub 2}O{sub 3}, the {alpha}-alumina phase can form at anomalously low temperatures.
Date: December 31, 1996
Creator: Veal, B. W.; Natesan, K.; Koshelev, I.; Grimsditch, M.; Renusch, D. & Hou, P. Y.
Partner: UNT Libraries Government Documents Department

Microstructures and Mechanical Properties of Two-Phase Alloys Based on NbCr(2)

Description: A two-phase, Nb-Cr-Ti alloy (bee+ C15 Laves phase) has been developed using several alloy design methodologies. In effort to understand processing-microstructure-property relationships, diffment processing routes were employed. The resulting microstructure and mechanical properties are discussed and compared. Plasma arc-melted samples served to establish baseline, . . . as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a ~ function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.
Date: December 7, 1998
Creator: Cady, C.M.; Chen, K.C.; Kotula, P.G.; Mauro, M.E. & Thoma, D.J.
Partner: UNT Libraries Government Documents Department

Orientation relationships in the system Nb-NbCr{sub 2}

Description: Two phase alloys are considered promising for structural applications. The orientation relationships between the phases can contribute to the mechanical properties of the material. A niobium-niobium/chromium{sub 2} eutectic alloy was prepared and the microstructure characterized.
Date: May 1, 1997
Creator: Kotula, P.G.; Chen, K.C. & Thoma, D.J.
Partner: UNT Libraries Government Documents Department

Electronic effects at interfaces in Cu-Cr, Mo, W, Ta, Re multilayers

Description: Interfacial electronic effects between Cu and the transition metals Cr, Mo, W, Ta, Re, are investigated by determining the strength of the white line absorption resonances on the L,,, edges of Cu in Cu{sub 5}/TM{sub 5} multilayers. X-ray absorption (XAS) was performed to study the white lines, which are directly related to the unoccupied states of Cu in the multilayers. The metallic multilayers are 2 mn in period and 200 mn in total thickness. Each period contains 5 monolayers of Cu and 5 monolayers of the transition metal: 40% of the atoms are at interfaces. These material pairs form ideal structures for the investigation of interfacial electronic effects as they form no compounds and exhibit terminal solid solubility. Only weak white lines are observed on the L3,2 edges of Cu since all the d-orbitals are filled. In the Cu/TM multilayers, however, we observed enhancement of the Cu white lines. We attribute this to the charge transfer from the `interfacial Cu atoms` d-orbital to the transition metal layers. Analysis of the white line enhancement enables calculation of the charge transfer from the Cu to the transition metal. Cu shows a charge transfer of about 0.03 electrons/interfacial Cu atom in Cu/Cr, 0.064 in Cu/Mo, 2048 0.35 in Cu/Ta, 0.17 in Cu/W , and 0.23 in Cu/Re. This charge transfer is consistent with the enhanced absorption energy of Cu on these materials as observed in thermal desorption experiments.
Date: April 1, 1998
Creator: Bello, A.F.; Van Buuren, T.; Kepesis, J.E. & Barbee, T.W., Jr.
Partner: UNT Libraries Government Documents Department

Refracted x-ray fluorescence (RXF) applied to the study of thermally grown oxide scales on Fe-Cr-Ni-(RE) alloys.

Description: Refracted X-Ray Fluorescence (RXF) is applied to the study of the thermally grown scales on Fe25Cr20Ni(RE) alloys. The evolution of chromia scales is investigated for alloys containing reactive elements (RE) Y and Zr as well as the corresponding RE-free alloy. For these alloys, scale compositions, scale thicknesses and growth rates are measured and information about concentration depth profiles is obtained.
Date: June 3, 1998
Creator: Koshelev, I.
Partner: UNT Libraries Government Documents Department

Room and elevated temperature mechanical properties of PM TiAl alloy Ti-47Al-2Cr-2Nb

Description: A TiAl alloy powder with the composition Ti-47Al-2Cr-2Nb (at. %) was prepared by rotary atomization, followed by hot-extrusion and subsequent heat treatments to produce refined lamellar structures and fine duplex structures. The mechanical properties of the TiM alloy were determined at temperatures to 1000C in air, and the microstructures were characterized by TEM, SEM, and electron microprobe analyses. The alloy with the refined lamellar structure showed excellent mechanical properties at both room and elevated temperatures. It exhibited a plastic strain of 1.4% and a yield strength of 971 MPa (140.9 ksi) at room temperature. The yield strength remained approximately constant up to 800C and decreased to 577 MPa (83.7 ksi) at 1000C. The transverse fracture toughness, estimated by three-point bend testing of chevron-notched specimens at room temperature, was 22.4 MPa {radical}m. The refined lamellar structure contained long and straight alternating {alpha}{sub 2} and {gamma} platelets with an extremely fine interlamellar spacing (0.1 {mu}m) and {alpha}{sub 2}-to-{alpha}{sub 2} spacing (0.22 {mu}m). The mechanical properties of the alloy have been correlated with the unique microstructures developed by hot extrusion.
Date: July 1, 1995
Creator: Liu, C.T.; Maziasz, P.J.; Schneibel, J.H.; Sikka, V.K.; Wright, J.; Walker, L.R. et al.
Partner: UNT Libraries Government Documents Department

Mechanically reliable surface oxides for high-temperature corrosion resistance

Description: Corrosion is widely recognized as being important, but an understanding of the underlying phenomena involves factors such as the chemistry and physics of early stages of oxidation, chemistry and bonding at the substrate/oxide interface, role of segregants on the strength of that bond, transport processes through scale, mechanisms of residual stress generation and relief, and fracture behavior at the oxide/substrate interface. Because of this complexity a multilaboratory program has been initiated under the auspices of the DOE Center of Excellence for the Synthesis and Processing of Advanced Materials, with strong interactions and cross-leveraging with DOE Fossil Energy and US industry. Objective is to systematically generate the knowledge required to establish a scientific basis for designing and synthesizing improved protective oxide scales/coatings (slow-growing, adherent, sound) on high-temperature materials without compromising the requisite properties of the bulk materials. The objectives of program work at Argonne are to (1) correlate actual corrosion performance with stresses, voids, segregants, interface roughness, initial stages of oxidation, and microstructures; (2) study such behavior in growing or as-grown films; and (3) define prescriptive design and synthesis routes to mechanically reliable surface oxides. Several techniques, such as Auger electron spectroscopy, X-ray diffraction, X-ray grazing incidence reflectance, grazing-angle X-ray fluorescence, optical fluorescence, and Raman spectroscopy, are used in the studies. Tne project has selected Fe-25 wt.% Cr-20 wt.% Ni and Fe-Cr-Al alloys, which are chromia- and alumina-formers respectively, for the studies. This paper presents some of the results on early stages of oxidation and on surface segregation of elements.
Date: May 1, 1995
Creator: Natesan, K.; Veal, B.W.; Grimsditch, M.; Renusch, D. & Paulikas, A.P.
Partner: UNT Libraries Government Documents Department

The correlation between swelling and radiation-induced segregation in iron-chromium-nickel alloys.

Description: The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is estimated using diffusivities derived from grain boundary segregation measurements in irradiated iron-chromium-nickel alloys. The resistance to void swelling in iron- and nickel-base alloys correlates with the segregation and both are functions of bulk alloy composition. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted. Additionally, swelling is shown to be greater in alloys in which the RIS profiles are slow to develop.
Date: March 5, 1998
Creator: Allen, T. R.; Busby, J. T.; Kenik, E. A. & Was, G. S.
Partner: UNT Libraries Government Documents Department

Growth of alumina scale on Fe-Cr-Al : a multiprobe study.

Description: The use of local probes at specific spatial locations provides a clear picture of the scale growth. The thermal evolution of the oxide scale on 72Fe-18Cr-10Al-0.15Hf (at.%) has been investigated using a number of spectroscopic techniques. Well defined regions ({approx}70 mm in diameter) were probed by a battery of techniques as a function of oxidation at different temperatures (Between 800 C--1100 C). This study provides information about the dependence of scale evolution on fluctuations in the local composition and/or grain structure of the starting material. Results suggest that properties of the starting material, which were not investigated in this study, strongly influence the scale evolution, even to the stage of mature scales.
Date: June 3, 1998
Creator: Veal, B. W.
Partner: UNT Libraries Government Documents Department